Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$146.93	10.550%	$162.4311	$162.43	$162.45	$162.40
Purchase #2	$92.42	7.670%	$99.5086	$99.51	$99.50	$99.50
Purchase #3	$29.64	8.141%	$32.053	$32.05	$32.05	$32.10
Purchase #4	$13.67	10.255%	$15.0719	$15.07	$15.05	$15.10
Purchase #5	$217.30	13.584%	$246.818	$246.82	$246.80	$246.80
Purchase #6	$243.45	6.322%	$258.8409	$258.84	$258.85	$258.80
Purchase #7	$75.55	3.480%	$78.1791	$78.18	$78.20	$78.20
7 purchase totals =	$818.96		$892.9026	$892.90	$892.90	$892.90